Introduction The optimal duration of antibiotic therapy for community-acquired pneumonia (CAP) is unsettled. Short-course therapy has proved successful in clinical trials but is not yet implemented in everyday clinical practice. Validation of results from randomised controlled trials is crucial to evaluate existing evidence and provide clinicians with assurance of using new treatment strategies. In a pragmatic framework, we aim to assess the use of short-course antibiotic therapy guided by the onset of clinical stability in patients hospitalised with CAP. Methods and analysis This study is a randomised controlled trial with a non-inferiority design that will examine the efficacy of short-course antibiotic therapy in patients hospitalised with CAP. From six hospitals across Denmark, we plan to enrol 564 patients between 2019 and 2024. Within 3-5 days after initiating antibiotic therapy, participants will be randomised 1:1 to parallel treatment arms: (1) short-course antibiotic therapy of 5 days or (2) antibiotic therapy of at least 7 days. The primary outcome will be 90-day readmission-free survival and will be estimated as an absolute risk difference with a predefined non-inferiority margin of -6%. Secondary outcomes will comprise other safety measures including new antibiotics, adverse events, length of hospital stay and postdischarge outpatient visits. Both intention-to-treat and per-protocol analyses will be performed. Ethics and dissemination This study has been approved by the Health Research Ethics Committee of the Capital Region of Denmark (identifier number: H-19014479). Trial data will be made available in anonymous form when the trial has ended. Trial registration number NCT04089787, ClinicalTrials.Gov.